title: Neuropeptidergic input pathways to the circadian pacemaker center of the Madeira cockroach analysed with an improved injection technique.
abstract: Light entrainment pathways synchronize the circadian clock of almost all species of the animal and plant kingdom to the daily light dark cycle. In the Madeira cockroach Rhyparobia (Leucophaea) maderae, the circadian clock is located in the accessory medulla of the brain's optic lobes. The clock has abundant neuropeptides with unknown functions. Previous studies suggested that myoinhibitory peptides (MIPs), orcokinins (ORCs), and allatotropin (AT) take part in light input pathways to the circadian clock. As the sequences of AT and ORCs of R. maderae have not yet been determined, with matrix-assisted laser desorption/ionization-time of flight mass spectrometry, the respective Rhyparobia peptides were characterized. To search for light-like phase-shifting inputs to the circadian clock, Rhyparobia-MIP-1, Rhyparobia-AT, and Rhyparobia-ORC were injected at different circadian times, combined with locomotor activity assays. An improved, less invasive injection method was developed that allowed for the analysis of peptide effects within <2 weeks after injection. Rhyparobia-MIP-1 and Rhyparobia-AT injections resulted in dose-dependent monophasic phase response curves with maximum delays at the beginning of the subjective night, similar to light-dependent phase delays. In contrast to Manduca sexta-AT, Rhyparobia-AT did not phase advance locomotor activity rhythms. Only injections of Rhyparobia-ORCs resulted in a biphasic light-like phase response curve. Thus, it is hypothesized that Rhyparobia-MIP-1 and -AT are candidates for relaying light-dependent delays and/or non-photic inputs to the clock, whereas Rhyparobia-ORCs might be part of the light-entrainment pathways relaying phase delays and advances to the circadian clock of the Madeira cockroach.
authors.affiliation: Department of Biology, Animal Physiology, University of Kassel, Heinrich-Plett-Str. 40, Kassel, 34132, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Schulze
authors.forename: Thomas
authors.initials: T
authors.lastname: Schendzielorz
authors.forename: Susanne
authors.initials: S
authors.lastname: Neupert
authors.forename: Reinhard
authors.initials: R
authors.lastname: Predel
authors.forename: Monika
authors.initials: M
authors.lastname: Stengl
mesh_terms: D000818:Animals; D057906:Circadian Clocks / Q000187:drug effects; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D003058:Cockroaches; D007267:Injections / Q000379:methods; D007301:Insect Hormones / Q000737:chemistry / Q000494:pharmacology; D019476:Insect Proteins / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009479:Neuropeptides / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D009899:Optic Lobe, Nonmammalian / Q000502:physiology*; D020539:Sequence Analysis, Protein
chemical_list: D056925:Circadian Rhythm Signaling Peptides and Proteins; D007301:Insect Hormones; D019476:Insect Proteins; D009479:Neuropeptides; C079067:orcokinin; C050669:allatotropin
keywords: Rhyparobia (Leucophaea) maderae; circadian behavioral assay; matrix-assisted laser desorption/ionization-time of flight; neuropeptides